By building “fairy circles,” termites engineer their own ecosystem

These barren circles allow water to collect in the desert.

The Namib Desert is dotted with thousands of mysterious “fairy circles,” which are near-perfect circles of barren soil two to fifteen meters wide, rimmed by tall grass. They are unmistakable and stretch for miles, giving the landscape an ethereal and otherworldly feel. Many possible explanations have been proposed, including toxic substances in the soil, meteorites, termites, UFOs, and the ghosts of dead natives. But the circles are extremely remote—more than 110 miles from the nearest village—and have been difficult to study scientifically. Despite decades of research, the cause of these bizarre circles has remained elusive.

But now, after a six-year study and more than 40 trips to the Namib Desert, Dr. Norbert Juergens believes he has come to understand the biological underpinnings of this strange phenomenon. According to Juergens, a single species of termites is responsible for creating and maintaining the circles. But the barren circles aren't just a byproduct of these tiny insects living below the sandy desert surface; they are part of a carefully cultivated landscape that helps the termites—and many other organisms—thrive in an otherwise inhospitable climate.

Juergens hypothesized that if the fairy circles’ cause was biological, the organism would need to co-occur with the circles and would probably not be found elsewhere. Only one species fit the bill: Psammotermes allocerus, the sand termite. Not only was the sand termite the only insect species that lived across the entire range of the fairy circles, but these termites were found to be living beneath nearly every circle sampled. And the harder the termites worked – foraging, burrowing, and dumping their refuse – the more grass died, leading Juergens to conclude that the termites keep the circles barren by burrowing underground and foraging on the roots of germinating grasses.

But the story doesn’t end there. The particular structure of the fairy circles—bare soil edged by tall grass— isn't just a side effect of the insects’ hard work. Instead, this characteristic architecture is vital to the termites' success, and even plays a role in structuring the rest of the ecosystem.

Juergens found that the water content of the soil inside the circles was surprisingly high, even at the driest times of the year. Soil humidity between the circles, meanwhile, was much lower. It turns out that the barren ground within the circles allows water to percolate down through the sandy soil and accumulate underground, rather than being taken up by plants and lost via transpiration. The termites living below the circles benefit from this store of water in an otherwise parched desert that receives less than 4 inches of rain annually. Furthermore, perennial grasses also flourish around the circles, thanks to the underground water. The termites then feed on this surrounding grass, expanding their circles ever so slowly.

In essence, the termites are cultivating their own constant sources of water and food by creating and maintaining these circles. It’s a complicated phenomenon, and, more than likely, there’s no actual consciousness or planning involved on the part of the termites; they are just instinctually performing tasks that have been etched into their DNA over millions of years. However, the end result of the insects' behavior is a massive change in their habitat, a process that scientists call “ecosystem engineering.” Just like beavers, sand termites are altering the entire landscape for their own benefit. And, indirectly, they are also helping other species, since fairy circles have been found to increase biodiversity: a disproportionately large number of insects, reptiles, plants, and small mammals are found in and around the circles.

Earlier studies had investigated whether termites were responsible for the circles, but these scientists were looking for a species called harvester termites, and concluded that they played no role. Sand termites are secretive, don't have obvious nests or burrows, and may have eluded these researchers.

But despite this new information, there’s still a lot to learn about fairy circles: for instance, why plants don't grow very well in soil taken from the center of the circles, and what role other species may play in the creation and maintenance of the circles. But for now, we can put the UFO and ghost theories to rest, and acknowledge the humble sand termite for this incredible feat of ecosystem engineering.

Here is another interesting development regarding the reclamation of barren wasteland:Allan Savory: How to green the world's deserts and reverse climate changeNotice how Mr. Savory acknowledges that he was wrong decades earlier and did and still does put in the time and effort to try to correct the damage to various deserts to impressive results. What a refreshing change from the usual ear-plugging and ass covering you find too often from others.

I was recently introduced to a new term. Can't easily find a reference for this on-line. A local plant enthusiast referred to a nearby park as containing "maple deserts". I'm not 100% sure what he meant, I think it mostly means a lack of understory plants under maple trees. My uniformed guess is that maples aren't any better at shading out competing plants, but the soil within reach of their roots is very, very dry. I think they compete by sucking all the surface water away from other plants, even to the point of wasting it.

Plants prevent the water from percolating into the deep soil. Instead they take it up and transpire, returning the water to the air. The retention you are taught is the failure of the water to drain away into deeper layers replenishing aquifers and other subsurface water deposits.

Barren sandy soil does not hold the water, instead the water percolates into deeper layers where it is protected from the heat of the surface layers. Without vegetation to draw it out and return it to the surface, these deep soil layers stay "damp" for long periods.

I was recently introduced to a new term. Can't easily find a reference for this on-line. A local plant enthusiast referred to a nearby park as containing "maple deserts". I'm not 100% sure what he meant, I think it mostly means a lack of understory plants under maple trees. My uniformed guess is that maples aren't any better at shading out competing plants, but the soil within reach of their roots is very, very dry. I think they compete by sucking all the surface water away from other plants, even to the point of wasting it.

Walt

This ABC News story may be related. Maples are some of the many trees that use chemical weapons to better their situation.

It’s a complicated phenomenon, and, more than likely, there’s no actual consciousness or planning involved on the part of the termites; they are just instinctually performing tasks that have been etched into their DNA over millions of years.

I was recently introduced to a new term. Can't easily find a reference for this on-line. A local plant enthusiast referred to a nearby park as containing "maple deserts". I'm not 100% sure what he meant, I think it mostly means a lack of understory plants under maple trees. My uniformed guess is that maples aren't any better at shading out competing plants, but the soil within reach of their roots is very, very dry. I think they compete by sucking all the surface water away from other plants, even to the point of wasting it.

Just wanted to say this is a good write up of this article and something I would have missed if not for Ars. This is why I like Ars.

Dammit, paleo. You beat me to it. Ars' tech-related coverage is top notch and would be enough to keep me coming back, but it's this kind of article feeding the general curiosity of us geeks that really sets Ars apart. Kudos to Ars and Dr. Shaw.

"But for now, we can put the UFO and ghost theories to rest, and acknowledge the humble sand termite for this incredible feat of ecosystem engineering."

Not so fast. The termite hypothesis is still just one of many:

"Other unsupported hypotheses included radioactivity, allelopathy and termite activity (all reviewed in [2]. Several authors [1], [3], [4], [7], [8], [9] proposed some version of causation by termites either through direct action, residual effect or emission of a toxic agent. However, Tschinkel [10] found no association between the nests or underground foraging tunnels of the endemic termite Baucaliotermes hainseii and fairy circles, nor have other termite species been found to be associated with fairy circles [2], [9]."

Clearly, we need to perform a double blind experiment to find out if this is the correct theory. It would be simple:

Create four equal areasIn one area, do nothingIn one area, apply an inert chemical (are there any of these?)In one area, apply an insecticide specific to the termite in question.In the last area, apply every dangerous chemical we know of to get rid of all living things (did someone say Neutron Bomb?)

Have observers who do not know how each area was treated report on the size and vitality of the circles.

If the results are conclusive, we are done. If not, we will have to destroy something else to get to the bottom of this. Sooner or later, we will know the cause, grow tired of the effort, or destroy the entire ecosystem.

"However, Tschinkel [10] found no association between the nests or underground foraging tunnels of the endemic termite Baucaliotermes hainseii and fairy circles, nor have other termite species been found to be associated with fairy circles [2], [9]."

"However, Tschinkel [10] found no association between the nests or underground foraging tunnels of the endemic termite Baucaliotermes hainseii and fairy circles, nor have other termite species been found to be associated with fairy circles [2], [9]."

Then again, this is a different species of termite and it HAS been found associated with these fairy circles. This new study is also almost a year more current.

Still valid. Termites MAY be the cause -but there is far from a clear consensus on this.From March 28th report: http://news.sciencemag.org/sciencenow/2 ... olved.html""...The link between foraging activity of the termite resulting in the formation of a perfect circle of bare soil is unclear."

Tschinkel agrees. "Juergens has made the common scientific error of confusing correlation—even very strong correlation—with causation," he says. "If Juergens claims termites are killing the grass, he's got to show that they're actually attacking living plants. That's not easy to do, and he didn't do it."

"My view is that fairy circles have little, if anything, to do with termites," agrees Michael Cramer, a plant ecophysiologist at the University of Cape Town. He now has a manuscript in review proposing that fairy circles are the product of natural vegetation patterns resulting from competition for scarce resources. "The only way for this question to be properly answered," he says, "is with more thorough investigations and focused experiments."

In a BBC documentary called Africa, David Attenborough mentions these "fairy circles" in the Namib desert and says that "we don't really know how they're made". Plenty of theories float around as pubert above pointed out, but this one is the most convincing.

Just wanted to say this is a good write up of this article and something I would have missed if not for Ars. This is why I like Ars.

Dammit, paleo. You beat me to it. Ars' tech-related coverage is top notch and would be enough to keep me coming back, but it's this kind of article feeding the general curiosity of us geeks that really sets Ars apart. Kudos to Ars and Dr. Shaw.

I did read about the paper in the BBC sci/health section but the article was much shorter and comments on Ars is where you really learn things.

I saw these circles featured on BBC Africa just the other day (jaw-dropping series, by the way). I was so surprised to hear that the cause was still debated. Thanks for covering what appears to be a likely explanation. Very timely

Kate Shaw Yoshida / Kate is a science writer for Ars Technica. She recently earned a dual Ph.D. in Zoology and Ecology, Evolutionary Biology and Behavior from Michigan State University, studying the social behavior of wild spotted hyenas.